1. Field of the Invention
One aspect of the invention relates to an electronic apparatus configured to adjust the luminance of the display screen according to the illuminance therearound.
2. Description of the Related Art
In electronic apparatus such as cell phones and cameras, to make the display screen easy to see, the light-emission luminance of the display screen is controlled so as to have an optimum value for the ambient illuminance. In this connection, there is an apparatus that is reduced in power consumption (see JP-A-2008-219659 (paragraphs 0029 and 0031 and FIGS. 7 and 8), for instance). In JP-A-2008-219659 (FIG. 7 and paragraph 0029), the battery operation time is elongated by reducing the power consumption by making the luminance of a backlight of a display module lower when the residual energy of a battery is small than when the residual energy is large. Furthermore, in JP-A-2008-219659 (FIG. 8 and paragraph 0031), during daytime when there is a large difference between illuminance in the sun and that in the shade, that is, a rapid variation occurs in ambient illuminance, a luminance control is employed in which the luminance control cycle is shortened to quickly respond to a rapid luminance variation.
There is another apparatus that is reduced in power consumption (see JP No. 2,891,955 (Pages 1-3 and FIGS. 1 and 2), for instance). In JP No. 2,891,955, the average power consumption of a processor etc. for calculating optimum luminance is reduced by turning on the power to the processor etc. intermittently rather than all the time using a timer. Same as in JP-A-2008-219659, the control can follow an illuminance variation by a variable setting of the timer cycle that the timer cycle is set long in an environment with a small illuminance variation and short in an environment with a large illuminance variation (JP No. 2,891,955, paragraph 0015).
The apparatus of JP-A-2008-219659 can elongate the battery operation time by reducing the power consumption by lowing the luminance of the backlight of the display module when the battery residual energy is small. However, a problem may arise that during such a control the display screen is reduced in luminance and hence made difficult to see.
In the apparatus of JP No. 2,891,955, the power consumption of the processor etc. for calculating optimum luminance is reduced. However, the power used for the light emission of the display module is much larger than that consumed by the processor etc. For example, where the display module is an LCD or the like, very large power is consumed for the light emission of the backlight. In the case of organic LEDs or the like, very large power is supplied for the light emission of the organic LEDs.